The L1 is an LED light so it doesn't have a replaceable bulb. If you are ambitious and have some electrical skills you could do a more in-depth mod to it, but you can't just stick a different bulb in there.
Well...you can doas NBP said, but, there are other options...first off, what Generation is it? Care to post a couple of pics of the front (lens) and side? If it's the most recent gen, you can get more juice out of it by throwing an RCR in it. If it's an older model, you can throw a newer model head on it. Then there's always Milky if you want a real barn burner.
Mine has a 5000k tint XM-L and I also did an XP-G HCRI mod on another members, The mod wasn't too hard to do but opening the head is really the PITA part IMO.
It's hard to tell from the beamshots because they are so close to the wall, but it appears to be brighter. Is that correct or does it just have a wider hotspot?
Ok lets try this. My Stone White (but dirty) 07 Magnum is 25 feet away set to manual, night scenery and ISO100. Again, all lights on highest setting, LX2 and V10R are running primaries and the others rechargeable. It's also rainy out.
Stock V10R Ti XP-G
HDS 140GT before step down
LX2
SC600w
L1 XM-L 5000k
The L1 is brighter to me in person but the LX2 is the clear winner of throw in this group.
I hope these are more useful, I'm still learning the camera thing.